I! I i *> \ i 1156 Appendix VI. The calorific value is about no B.T.U. per cub. ft., and one volume is mixed with 1-13 of air in the engine, for which propor- tions the valves must be designed. The Simplex engine (p. 701) has been enlarged for blast-furnace gas, an example of 700 H.P. being shewn at the Paris Exhibition of 1900, and Fig. 1021 illustrates a complete plant for the supply and treatment of the s&g^^\-asiy^^>ys^^^ TeT H EQUILIBRIUM we h PlasiL. gas, where A A are washers, B B condensers to eliminate moisture, c c scrubbers to remove ammonia, and D p sawdust filters. The holder E stores the purified gas, and passes it on to the engine F. Natural gas is obtained in petroleum districts, and its compli- cated composition is given by the following average:— H ...... 27-8 CH4 . ..... 6r8 C2H6 ...... 7-8 QH4 ...... •5 CO ..... , •6 C02 .,..., 5 j- diluents. 1*0 J loo'o parts by volume, shewing a rick gas with but few non-combustibles.